Two-layer Composites Research Articles

Two-Layered Microwave Absorber Laminated with Magnetic Composites for Intelligent Transport System

Two-layered microwave absorbers are designed for the achievement of low reflection coefficient for wide angles of oblique incidence at the frequency of intelligent transport system (5.9 GHz). Magnetic composite sheets were fabricated with carbonyl iron (CI) and Co2Z hexaferrite particles in rubber matrix. On the basis of transmission line theory, reflection loss has been calculated with variation of incident angles for both transverse electric (TE) and transverse magnetic (TM) polarization. The minimum reflection loss (less than-20 dB) is predicted at 5.9 GHz for the laminated composites of Co2Z/CI. At the optimum thickness of the composite layers, a low value of reflection loss (less than-10 dB) is predicted for wide incidence angles up to 60°. The two-layer composites laminate can be proposed as the high potential microwave absorbers for improvement of electromagnetic environment in ITS operation.

Utilization of Albizia Wood (<i>Albizia falcat</i>a) and Ramie Fibers as Wind Turbine Propeller Modification of NACA 4415 Standard Airfoil

Ramie fibers and albizia wood, which are abundantly available in Indonesia, were used in fabricating hybrid sandwich composite for wind turbine propeller. A prototype was fabricated by modification of NACA 4415 standard airfoil, intended for low speed wind and environmental friendly operations. Hand lay-up method was applied for fabrication of this hybrid composite with one and two layers of ramie fiber. Mean volume fiber fraction (vf) of one-layer and two-layer composite are 47,12% and 44,82%, respectively. The highest measured bending stress is 30.88 MPa for two-layer composite with modulus of elasticity 2.02 GPa and bending strain 1,795%. Microstructure of this hybrid composite is unchanged significantly after 5.5 months operation. With ultimate simplicity and low manufacturing cost, hand lay-up method is suitable for small scale production.

Electromagnetic shielding properties of multilayered composites containing multiple inclusions with various spatial distributions

A scheme is proposed for predicting the electromagnetic shielding properties of multilayered composites containing multiple inclusions of diverse shapes, volume concentrations, and spatial distributions based on homogeneous comparison materials and the plane-wave shielding theory. This scheme leads to completely explicit formulas for the shielding effectiveness and reflected loss of multilayered composites in terms of microstructural parameters that characterize the shape, distribution, and orientation of the inclusions. The predicted shielding effectiveness and reflected loss of single layer composite containing randomly oriented and distributed flaky silver-coated carbonyl-iron particles and two-layer composite containing randomly oriented and distributed nickel-plated short carbon fibers agree well with the experimental data.

Magnetoelectric Properties of Two-Layered Composites Tb0.12Dy0.2Fe0.68 – PbZr0.53Ti0.47O3

At frequencies of the measuring magnetic field of 9.9–253 kHz over a temperature range from 79 K to 289 K the magnetoelectric effect in two-layered ferromagnetic-piezoelectric composites Tb0.12Dy0.2Fe0.68 – PbZr0.53Ti0.47O3 with ferromagnetic Tb0.12Dy0.2Fe0.68 and piezoelectric PbZr0.53Ti0.47O3 layers of 6 × 6 × А mm3 (A = 0.6, 0.9, and 1.2) and 8 × 6 × 0.3 mm3 in size, respectively, has experimentally been studied. Resonant frequencies of bending and longitudinal oscillations of composite samples of Tb0.12Dy0.2Fe0.68 – PbZr0.53Ti0.47O3 have been calculated. We have studied dependences of the magnetoelectric effect in composites on a frequency of the measuring magnetic field, a thickness of a Tb0.12Dy0.2Fe0.68 layer, the bias magnetic field strength, and temperature.

Eigenvalue problems modelling the stability of a plane-parallel shear in a two-layer viscous composite

We present the derivation of a precise statement of a linearized eigenvalue problem that models the stability of a plane-parallel shear flow in a composite consisting of two different layers of heavy Newtonian media. The peculiarities of the influence on the stability of five dimensionless criteria participating in the equations and boundary conditions are discussed. The specific feature of the power conditions of contact is that a spectral parameter α enters these conditions nonlinearly.

The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties

III–V growth and surface conditions strongly influence the physical structure and resulting optical properties of self-assembled quantum dots (QDs). Beyond the design of a desired active optical wavelength, the polarization response of QDs is of particular interest for optical communications and quantum information science. Previous theoretical studies based on a pure InAs QD model failed to reproduce experimentally observed polarization properties. In this work, multi-million atom simulations are performed in an effort to understand the correlation between chemical composition and polarization properties of QDs. A systematic analysis of QD structural parameters leads us to propose a two-layer composition model, mimicking In segregation and In–Ga intermixing effects. This model, consistent with mostly accepted compositional findings, allows us to accurately fit the experimental PL spectra. The detailed study of QD morphology parameters presented here serves as a tool for using growth dynamics to engineer the strain field inside and around the QD structures, allowing tuning of the polarization response.

Physical fundamentals of mesomechanics of a two-layer composite: Development of fatigue cracking

Physical fundamentals of mesomechanics of a two-layer composite: Development of fatigue cracking

Geometry effect on mechanical properties of woven fabric composites

The effects of geometry on mechanical properties in woven fabric composites were explored. Two types of composites, including one-layered and two-layered composites, were designed and studied. For one-layered composites, inter-strand gap effects on the mechanical properties were studied, while three cases of geometries with inter-strand gaps in two-layered composites were evaluated. A woven fiber micromechanics analytical model called MESOTEX was employed for theoretical simulation. The predicted results show that the inter-strand gap and simple variation of the strand positions in a repeating unit cell significantly affect the mechanical properties of woven fabric composites.

A modification of the least-squares method in the identification problem for elastic laminated composites

A modification of the least-squares method is proposed in the identification problem for elastic two-layer composites. This modification is compared with the standard least-squares method for various models of materials.

Laws governing the dynamic fracture of two-layer bimetallic composites

A study was made of the impact toughness of three series of Charpy specimens that were cut from a continuous-caster roller and contained stress concentrators having different orientations relative to the hard-facing on the roller. Tests were performed on an automated impact tester. The steel with a ferrite-pearlite structure (steel 35G2) was found to have a higher impact toughness than steel with a ferrite-martensite structure (steel 18Kh11MNFB). The effect of microstructure on crack growth in the bimetal was studied experimentally for different types of steels. The results that were obtained can be used to check the impact toughness of hard-facings.

An Integral Approximate Solution to Ablation of a Two-Layer Composite with a Temporal Gaussian Heat Flux

Ablation is the most common approach for thermal management for reentry of the spacecraft to the atmosphere. An analytical solution of the ablation of a two-layer composite, which includes an ablative layer and a nonablative substrate, subject to a Gaussian heat flux is presented in this paper. The problem is divided into five stages and the temperature distributions in both layers in the five stages are obtained using an integral approximate method. The locations of ablation interface, thermal penetration depth, and ablation rate are obtained and the effects of Stefan number, subcooling parameter, thickness of the ablative material, and ratio of thermal diffusivities between two materials are investigated.

Tensile Property of the Flax/Polyester Composites after Water Treatment

Flax fabric was woven and composites were produced by using the VARI technique with flax fabric as the reinforcement and unsaturated polyester as the matrix. Laminates with two, three and four layers were fabricated respectively. After saturated in the water for different durations of time (7, 14, 21 and 30 days), the tensile strength of the composites was tested. After being soaked in the water for 7, 14 and 21 days, the tensile strength of the two-layer composites was decreased. For the three and four layers specimens, the tensile strength was increased initially with water treatment for 7 and 14 days,and decreased for 21 and 30 days. Scanning electron microscopy (SEM) confirmed that it might be contributed to the thickness of the two-layer composites. The thinner specimen is easier to be damaged by the penetrated moisture owing to the delamination between the fiber and the matrix after water immersion. For the three and four layers specimens, their contradictory tensile strength suggests that the thicker specimen can delay the moisture permeation and is of better water durability.

Identification of elastic properties for two-layer composites

An identification method for evaluating the elastic properties of two-layer composites is proposed. The method is estimated for different parameter values.

Structure and microhardness of nanocrystalline composite alloys on the basis of Al and Ti

A nanotechnology for production of layered composite nanocrystalline Al-Si, Al(1Hf + 0.2Nb + 0.2Sn, wt %)-Si, Al(0.5Ce + 0.5Re + 0.1Zr, wt %)-Si, and Ti-Si alloys has been suggested. The structure of the nanocrystalline composites obtained has been studied by the methods of optical microscopy and scanning and transmission electron microscopy. Experimental data on the microhardness of layered composite nanocrystalline alloys on the basis of aluminum and titanium are given. The microhardness of the nanocrystalline two-layered Al-Si composite in comparison with submicrocrystalline aluminum increased by a factor of three. In the nanocrystalline two-layered Ti-Si composite (compacted from powders), the microhardness also increased by a factor of almost six in comparison with nanocrystalline titanium. In the nanocrystalline two-layered composite alloys of aluminum, the increase in microhardness in the case of the Al(Hf,Nb,Sn)-Si alloy was up to 45% as compared to the composite on the basis of the metallic foil and by a factor of two as compared to the powder-compact composite; and in the case of the Al(Ce, Re,Zr)-Si alloy, by a factor of 1.6 and 2.7, respectively. An increase in the number of layers in the composites had no significant effect on the level of microhardness.

Mechanical Properties of Laminated Biodegradable Plastics Composites Made with Mg Alloy as Reinforcement

To improve the mechanical properties of biological decomposition plastics, in this study, laminated reinforce plastics (LBRP) were made using AZ31 magnesium alloy as reinforcement, Bionolle as the base material, and an adhesion bonding agent based on cyanoacrylate and epoxy resin. The LBRP were laminated as one-layer and as two-layer composites using AZ31 magnesium alloy and Bionolle. The tensile strength of a layer of clad material increased with an increase in the volume fraction of Mg alloy, and was corresponding to rule of mixtures with mother and reinforced material. The strengths of the two-layer LBRP indicated were much greater than that assumed by the mixtures rule. Because the adhesion bonding agent flowed and bonded into the grooves of the conversion coating film, the tensile strength of the LBRP increased along with an increase in the arithmetical mean roughness on the conversion coating film. As a functional characteristic, a vibration test was carried out for these LBRP made with AZ31 magnesium alloy reinforcement, which has an excellent attenuation characteristic. In the result, the damping ratio and amplitude ratio for a layer of clad material are better than these for a base material. Therefore, the effect of the attenuation characteristic of AZ31 magnesium alloy is proved as beneficial in composites.

An expansion result for a Sturm-Liouville eigenvalue problem with impulse

The paper is concerned with an eigenvalue problem for second order differential equations with impulse. Such a problem arises when the method of separation of variables applies to the heat conduction equation for two-layered composite. The existence of a countably infinite set of eigenvalues and eigenfunctions is proved and a uniformly convergent expansion formula in the eigenfunctions is established.

Anisotropic Effect and the Crystals Nature on the Elastic Fields Dispersal Generated in a Three Layers Material

Semiconductor nanostructures are interesting objects for many microelectronic and optoelectronic applications. Nevertheless, to use them, it is necessary to control their size, their density and their spatial distribution. In the last decade, many researches have been done to control these parameters. One of these researches is the elaboration of a functional substrate inducing a lateral self-organization of nanostructures. The organization driving force is the strain field induced on the surface by a buried dislocations network. The purpose of this work is the numerical resolution, in the case of anisotropic elasticity, of the problem of a misfit dislocation located between an infinite substrate and two-layer composite. The elastic fields of stresses are calculated for various orientations of the Burgers vector, by inversion of 30x30 arrays of linear equations. The composite NiSi2/Si / (001) GaAs, that made the object of several investigations, is treated like example.

MAGNETODIELECTRIC EFFECT IN TWO-LAYER MAGNETOELECTRIC PZT-MZF COMPOSITE

ABSTRACT The magnetodielectric (MD) effect in two-layer composites consisting of polarized PbZr0.53Ti0.47O3 (PZT) ceramics and Mn0.4Zn0.6Fe2O4 (MZF) ferrite plates has been studied. The MD coefficient Δϵ/ϵ(0) was established to depend on a thickness of the magnetostriction layer, a bias magnetic field strength, and an electric field frequency. Using thermodynamic approach an inspection of obtained results for two-layer structure has been carried out.

Microwave absorbers of two-layer composites laminate for wide oblique incidence angles

Advanced microwave absorbers for wide oblique incidence angles are required in many applications including wireless communication or vehicle identification in Intelligent Transport System (ITS) where 5.8 GHz Dedicated Short Range Communication (DSRC) system is applied. In this study, two-layer microwave absorbers are designed for the achievement of low reflection coefficient over wide incidence angles at 5.8 GHz. The absorbing layer of rubber composite containing magnetic iron flake particles and the surface layer of low dielectric constant (carbon black composite and glass fiber composite) have been used in the absorber design. On the basis of transmission line theory, the reflection loss has been calculated with variation of incident angles for both Transverse Electric (TE) and Transverse Magnetic (TM) polarization. At the optimum thickness of the composite layers, a low value of reflection loss (less than −10 dB) has been predicted for wide incidence angles up to 60° for both TE and TM polarization, which is well consistent with the reflected power measured by free-space arch test. The two-layer composite laminate consisted of magnetic absorbing layer with high magnetic and dielectric loss and surface impedance-matching layer of a controlled dielectric constant can be proposed for high potential microwave absorbers in ITS.

Investigation of the plane stress state of a multilayer structure under heat variations

Now that composite materials are used in various fields of technology, their resistance to heat variations, which cause additional stresses because of noncoinciding layer thermal expansion coefficients, becomes increasingly topical. Apparently, the first study in this field was performed in [1], where the stress state in beam-like thermostats was determined. In [2], it was shown that delamination moments arise at the ends of two-layer beams, and the possibility of their influence on the process of delamination of two-layer composites was considered. In [3], in a similar setting, delamination stresses in multilayer structures were considered. In [4–7], the stresses at the edges of two-layer beams were calculated. We note that in all these papers the main assumptions of beam theory were used, which were confirmed experimentally for the analysis of beams. When studying the stress state near the ends of multilayer structures, the applicability of beam theory is doubtful, because the plane cross-section hypothesis, usually acceptable for beams, is justified only for the main part of the beam but not for areas near its ends, where the delamination process usually begins. The paper [8] essentially deals with a problem for a rectangle whose short sides are free from external loads and whose long sides are free from normal pressures; some longitudinal displacements imitating the temperature strains from the neighboring rectangles are given on the long sides. In [9, 10], the same problem was solved with the use of different mathematical representations of the Airy function, but the obtained numerical results practically coincide. In the present paper, we consider a system consisting of infinitely many alternating isotropic elastic layers with repeated elastic and thermal characteristics; these layers are represented as rectangles connected along the long sides.